What is a Customer and are they an asset or liability to the company?

customers are the persons who buy the products from the company..if they purchase products in cash then they give profits and increase asset of the company in form of cash...and if they purchase on credit basis then also they give profits and increase the asset of the co in form of debtors..also some customers default in payment when they take credit then it is known as bad debts which decrease the assets of the company..!